In the manufacture of gas turbine engines, and other complicated pieces of machinery, many components of the engine need to be inspected prior to assembly to ensure compliance with dimensional requirements. For example, after a component is produced, it is common practice to inspect the component using a coordinate measuring machine (CMM). An accurate and precise measurement of a finished component is desired to ensure uniformity and quality. It is well known in the industry that a dimension of a desired portion on a component can be measured by using datum points as references, which locate the part in the six degrees of freedom needed to fully constrain the part.
Generally speaking, during the manufacturing process, simple planar datum points are located directly on the component for primary machining purposes. In most instances, these same planar datum points are used during the inspection processes. However, the location choice of these planar datum points are typically chosen in a manner that is best suited for particular manufacturing processes without regard to usage of the planar datum points during the later inspection processes.
Not all inspections are as simple as using the planar datum points to take measurements of a finished component. In certain instances during the manufacturing processes, a component may be coated, in its entirety or in part, with a protective or ornamental material. Some of these coatings have a significant thickness to them, which needs to be accounted for when inspecting and correlating the dimensions of the component. For example, in the manufacture of airfoils for gas turbine engines, particularly aluminum airfoils, relatively thick coatings are applied to protect the airfoil from corrosion and erosion. While such coatings are effective, they present a challenge in terms of inspection.
As mentioned before, the planar datum points are typically chosen based on what is best for the manufacturing processes without regard to the inspection processes. This is true even when the component needs to be coated. Moreover, when choosing the location of the planar datum points on the component little effort is made in marking the datum points in a location that avoids coating over the datum points. Particularly, such prior art techniques present a problem in that the coating over the planar datum points prevents the datum points from being used when correlating pre-coated dimensions to post-coated dimensions during inspection.
Thus, there is a need for a method of transferring datum points from a pre-coated state of a component to a post-coated state of the component to expedite the inspection process.